Running Torque

Running torque is the amount of torque required to keep a fastener turning once it has started moving, typically measured without the fastener fully clamping a joint. In other words, it describes the “turning resistance” in the threads during installation or removal, separate from the torque used to create final clamp load. Running torque is commonly discussed with prevailing-torque locknuts, patch-coated screws, nylon-insert nuts, and other locking features that intentionally add friction.

Running torque matters because it affects both assembly effort and the ability of a fastener to resist loosening from vibration. For locking fasteners, specifications may define an acceptable running torque range to ensure the locking feature is strong enough to hold but not so high that it causes installation problems or damages the fastener. It can also be influenced by lubrication, coatings, surface finish, thread tolerance, and reuse; for example, a nylon insert or thread patch may have higher running torque on the first installation and lower running torque after multiple uses.